In three-dimensional (3D) ultrasound imaging, also called volume imaging, the acquisition of a 3D-image is accomplished by conducting many two-dimensional (2D) scans that slice the volume of interest in an anatomical region. Hence, a multitude of 2D-images is acquired that lie one next to one another. This multitude of 2D-images together forms a 3D-volume of data. By proper image processing, a 3D-image of the volume of interest can be built out of the 3D-volume of data. The 3D-image can then be displayed in a proper form on a display for the user of the ultrasound imaging system.
Ultrasound imaging is commonly used to image the insertion, use or operation of an invasive medical device or instrument within the body. For example, fine needle aspiration (FNA), core biopsy, radio frequency ablation (RFA), percutaneous ethanol injection (PEI) are all procedures that require insertion of an invasive medical device into the patient. Such a procedure using ultrasound imaging is commonly referred to as ultrasound image guidance procedure. When performing such image guidance procedure, the doctor must be able to visualize the target (e.g. a carcinoma to be ablated in RFA) in the anatomical region, the invasive medical device (e.g. needle) approaching the target, and any vessels surrounding the target, in particular blood vessels (also called vasculature). Imaging of the vessels is key for ensuring that no major vessel is punctured during the insertion and guidance of the invasive medical device. Therefore, the doctor or clinician commonly relies on using ultrasound image guidance to insert an invasive medical device, such as a biopsy needle or an ablation probe, into a patient, for both diagnosis and treatment. Ultrasound image guidance is important because it helps the doctor or clinician to visualize and hence plan the path of the invasive medical device from the skin to the target (e.g. target lesion), while avoiding blood vessels along the way.
Most of the ultrasound image guidance is done under 2D B-mode ultrasound. This is primarily because frame rates are high in 2D B-mode ultrasound. B-mode generally refers to a mode of operation in which the display shows a grayscale image representing the 2-dimensional distribution of ultrasound backscatter amplitude from one plane or slice of the target, which is formed by detecting the returning echoes for each of a series of acquisition lines across the image plane (typically one transmit pulse per line). It is quite critical to reduce any time lag between what is shown on the display and what is actually happening with the invasive medical device (e.g. needle) in the patient's body. A slow frame rate and accordingly a delayed ultrasound image feedback may result in the invasive medical device (e.g. needle) missing in the intended anatomical region. This can limit the use of any flow imaging techniques, which require the acquisition of many pulse-echo events per imaging line, such as for example color flow imaging or also called color Doppler imaging, during an ultrasound image guiding procedure. On the other hand, flow imaging provides a far better delineation of the vessel boundaries than the B-mode alone. In particular, 3D-flow imaging would be a good method for ensuring that vessels do not lie in the path of the invasive medical device (e.g. needle) since in 2D-imaging only a single plane is seen and it is typically difficult to keep the invasive medical device in the plane of the image at all times. However, frame rates in 3D-imaging, and especially 3D-flow imaging, are usually even more compromised than in the 2D-imaging.
US 2011/0263985 A1 discloses an ultrasound imaging system for creating simultaneous needle and vascular blood flow color Doppler imaging. A B-mode image of an anatomical area of interest is created. A first set of Doppler image data optimized for the visualization of vascular blood flow is created along one Doppler image processing path. A second set of Doppler image data optimized for the visualization of a needle or other invasive device is created among another, parallel Doppler image processing path. The color Doppler image is created, and then displayed, by combing some or all of the B-mode images, the first Doppler image data and the second Doppler image data based on a plurality of user selectable modes.
Such ultrasound imaging system uses B-mode ultrasound imaging and color Doppler imaging simultaneously. This reduces the frame rate. Therefore, there is a need for increasing or providing a sufficient frame rate in ultrasound image guidance procedures.